Known as construction machines employed in demolition work of structural objects, dismantling work of waste, civil engineering or construction work, and/or the like include those having an upperstructure mounted rotatably on an undercarriage, which can travel by a power system, and a multi-articulated front working mechanism attached pivotally up and down to the upperstructure and drivable by actuators. As one example of such working machines, there is a demolition work machine constructed by using a hydraulic excavator as a base. This demolition work machine includes a front working mechanism, which is comprised of a boom and arm and is connected pivotally up and down to an upperstructure, and a working attachment such as a grapple, bucket, breaker, crusher or the like attached to a free end of the arm, so that it can perform work such as demolition work of structural objects or dismantling work of waste.
Such a working machine performs work by variously changing its posture with a boom, arm and working attachment, which make up a front working mechanism, being kept extending to an outside of the upperstructure. The working machine may, therefore, lose a balance and tip over if an unreasonably aggressive operation is performed. It is, hence, required for an operator to safely perform the work while precisely grasping the current stability or tipping risk of the working machine. The term “stability” as used herein means how stably a working machine can continue work on a work surface without tipping.
For such a requirement, there is disclosed, for example, in Patent Document 1 a system that calculates a center of gravity of a crawler crane and a load applied thereon from output values of load indicators arranged at stabilizer parts of the crawler crane and clinometers arranged on a crawler, and further, that determines in which one of preset regions the calculated center of gravity is located and displays the center of gravity on a monitor by using a color designated specifically for that region.
As another example, Patent Document 2 discloses a system that is provided with stabilizer projection width sensors and stabilizer reaction force sensors, calculates a tipping limit from output values of the stabilizer projection width sensors, calculates degrees of risk to tipping at the front, rear, left and right from output values of the stabilizer reaction force sensors, calculates a combined center of gravity of a crane from the output values of the stabilizer projection width sensors and stabilizer reaction force sensors, displays them on a display, and, if there is a risk of tipping, triggers a warning, and further, fixes passive joint units of respective stabilizers to avoid tipping.